Next: IsLonAxis(axis) - Is the specified celestial axis a longitude axis?
Up: AST Attribute Descriptions
Previous: IsLatAxis(axis) - Is the specified celestial axis a latitude axis?
IsLinear
-
Is the Mapping linear?
- Description:
- This attribute indicates whether a Mapping is an instance of a
class that always represents a linear transformation. Note, some
Mapping classes can represent linear or non-linear transformations
(the MathMap class for instance). Such classes have a zero value for
the IsLinear attribute. Specific instances of such classes can be
tested for linearity using the
astLinearApprox function.
AST_LINEARAPPROX routine.
- Type:
- Integer (boolean), read-only.
- Class Applicability:
-
Mapping
-
All Mappings have this attribute.
-
CmpMap
-
The IsLinear value for a CmpMap is determined by the classes
of the encapsulated Mappings. For instance, a CmpMap that combines
a ZoomMap and a ShiftMap will have a non-zero value for its IsLinear
attribute, but a CmpMap that contains a MathMap will have a
value of zero for its IsLinear attribute.
-
Frame
-
The IsLinear value for a Frame is 1 (since a Frame is equivalent
to a UnitMap).
-
FrameSet
-
The IsLinear value for a FrameSet is obtained from the Mapping
from the base Frame to the current Frame.
Next: IsLonAxis(axis) - Is the specified celestial axis a longitude axis?
Up: AST Attribute Descriptions
Previous: IsLatAxis(axis) - Is the specified celestial axis a latitude axis?
AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk
Copyright (C) 2009 Science \& Technology Facilities Council